Electric circuit breaker with lock-open latch



y 26, 1964 G. E. GAUTHIER ETAL 3,134,879

ELECTRIC CIRCUIT BREAKER WITH LOCK-OPEN LATCH Filed June 20, 1962 2 Sheets-Sheet 1 INVENTOR. GEORGE EGAu'rmaR,

MAumcs EfiIROIS BY ATTdR/g y 1964 G. E. GAUTHIER ETAL 3,134,879

ELECTRIC CIRCUIT BREAKER WITH LOCK-OPEN LATCH 2 Sheets-Sheet 2 Filed June 20, 1962 INVENTOR- GEORGE- E.GAuTmzR,

M Aumcr-z E. SIROIS BY 0? M1?- C ATTORNEYQIDV United States Patent Ofi ice 3,134,879 Patented May 26, 1964 3,134,879 ELECTRIC cmcurr BREAKER WITH LOCK-OPEN LATCH George E. Gauthier and Maurice E. Sirois, Plainville,

Conn, assiguors to General Electric Company, a corporation of New York Filed June 2th, 1962, Ser. No. 203,926 1 Claim. (El. 290-169) Our invention relates to electric circuit breakers, and particularly to electric circuit breakers of the type including a spring-biased member releasably held by current-responsive means in position to maintain the movable contacts in closed circuit position. More particularly, the invention relates to such circuit breakers including means for preventing rebound of the movable contact members toward closed position following release of the releasable member.

In electric circuit breakers of substantial capacity, such as 800-1000 amperes, relatively heavy parts and heavy operating springs are required to maintain necessary contact pressure. When such an operating mechanism is released upon the occurrence of predetermined current conditions, to permit automatic opening, the movable contact members are moved to open position with extremely high speed. When striking the stops provided for such contact arms, the contact arms may rebound toward reclosed position, thereby creating danger of a restrike of the arc.

Various latching arrangements have been provided in accordance with the prior art to retain such movable contact members in the open position when automatic opening occurs. Such expedients have in general added substantially to the expense and difi'iculty of assembly and reliability of the circuit breaker.

It is an object of the present invention to provide an electric circuit breaker of the type described, having a movable contact member which is automatically movable to open circuit position upon the occurrence of predetermined current conditions wherein the circuit breaker includes latching means for retaining the movable contact member in automatically-opened position without the necessity of extra parts, and without requiring latching upon normal opening movement of the movable contact members.

In accordance with the invention, an electric circuit breaker is provided of the type having a pivotally movable contact arm and means for operating the contact arm to open and close circuit position comprising a pair of toggle links interconnected between the contact arm and the releasable support or cradle. A pivotally mounted manually operating handle is also provided having an overcenter tension spring connected between it and the knee of the aforesaid toggle for moving the toggle between collapsed and straightened positions. Furthermore, in accordance with the invention, the cradle member is provided with an integral extension or hook portion which, when the cradle moves to tripped position, maintains itself in a position to automatically engage the movable contacts when the contacts move to automatically opened position, whereby to retain the movable contact members in open position and prevent rebound.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claim.

In the drawings,

FIGURE 1 is a side elevation View of an electric circuit breaker incorporating the invention, the insulating casing being shown in section, and the parts of the mechanism being shown in closed circuit position;

FIGURE 2 is an enlarged elevation view of the op erating mechanism of the circuit breaker at FIGURE 1;

FIGURE 3 is a view similar to FIGURE 2, showing the parts in the automatically-tripped open position, and

FIGURE 4 is a perspective View of a portion of the operating mechanism of the circuit breaker of FIGURES 1 through 3.

Referring to FIGURE 1, the invention is shown as incorporated in an electric circuit breaker including an insulating casing having a base 10 and a cover 11. The circuit breaker shown comprises a three-pole circuit breaker having three side-by-side line terminals 12 (only one shown) supported on the base 10 at one end thereof, and three side-by-side load terminals 13 (only one shown) supported on the base 10 at the other end thereof. The construction of the circuit breaker at each of the poles is substantially identical, and therefore the current path between the terminals 12 and 13 will be described in detail in connection with only one such pole, i.e., the center pole.

The line terminal 12 is connected to a conductor strap 14, by suitable means, not shown. The conductor strap 14 carries a pair of side-by-side main contacts 15 (only one shown), and an arcing contact 16. A pair of cooperating movable main contacts 17 are provided, together with a movable arcing contact 18, the movable contacts 17 and 13 being pivotally supported by a pivot pin 19 on a movable contact arm 29. Suitable compression springs 21 are provided between each of the movable contacts 17 and 18 and the contact arm 20 to provide contact pressure. The contact arm 20 for the center pole is pivotally supported by pivot pin 22 in a mechanism frame 23.

The movable contacts 17 and 18 are connected by flexible electrical conductors 24 to a conductor strap 25 which in turn is connected to an input terminal 26 of a trip unit 27, to be described. The output terminal 28 of the trip unit 27 is connected to the load terminal 13.

The center contact arm 20 carries a contact cross-arm 29 to which the two outside movable contact arms are also rigidly connected by suitable means, not shown. A suitable arc extinguishing structure is also provided comprising ceramic side plates 30 and stacked metallic arc extinguishing plates 31.

For the purpose of operating the movable contact arm 20 and the two outside contact arms between open and closed circuit positions, operating mechanism is provided indicated generally at 32 (see FIGURES 2 and 3). The operating mechanism 32 comprises a releasable support or cradle 33 which is pivotally supported in the mechanism frame 23 (see FIGURE 1) by a pivot pin 34-. The cradle 33 has a releasable latched extension 35 at one end which is releasably held by a holding member 36 carried by the trip unit 27. The cradle 33 also has a hooklike extension 37 at its opposite end, for a purpose to be described.

The operating mechanism 32 also includes an interconnected pair of toggle links 38 and 39 which are connected to each other and to the cradle and center contact arm 20 by pins 46, 41 and 42 respectively. An operating handle 43 of insulating material is also provided supported on a handle support member 44 which is pivotally supported on pivotal supports 45 carried by the mechanism frame 23. A tension type operating spring 46 is connected between the operating handle support 44 and the knee pin 40 of the toggle links 38, 39.

In operation, when the cradle member is in latched engagement with the latch 36, and the handle is in the position shown in FIGURE 1, the tension spring 46 maintains the knee of the toggle in such position as to maintain the toggle links 38, 39 in straightened condition, thereby holding the contact arms 20 in circuit closed position compressing the contact pressure springs 21. When the handle is moved to the extreme counterclockwise posi- 8 3 tion, not shown, the tension spring 46 is moved across the pivot pin 41, thereby causing the toggle links 38, 39 to assume a collapsed position and moving the contact arms 20 to an upward or open circuit position.

The tripping operation occurs when the cradle member 33 is released from the latch member 36 by action of the trip unit 27. When this occurs, the force of the tension spring 46 acts on the cradle member 33, through the toggle link 38 to cause clockwise rotation of the cradle member as viewed.

In order to prevent rebound of the movable contact arms 20 from the tripped-open position, latch means is provided, comprising a hook-like extension 37 carried by the releasable cradle member 33. For this purpose, the center contact arm 20 is provided with a slot like opening 20A (see FIGURE 2). So long as the cradle member 33 is retained in latched position as shown in FIGURES 1 and 2, the movable contact arm moves in such a way that the opening 20A coincides with the position of the hook-like extension 37 of the cradle 33, as indicated in dotted lines in FIGURE 2. The hook 37 therefore has no effect upon the contact arm 20 in these circumstances.

Upon release of the cradle member 33 by the trip unit 27, however, it rotates to the clockwise position as shown in FIGURE 3. This moves the hook member 37 into the path of movement of the contact arm 20. A portion of the contact arm 20 adjacent one end of the slot 20A, therefore engages the cam surface 37a of the hook extension 37. The effect of the engagement of the contact arm 20 with the cam surface 37a of the cradle member 33 is such as to cause a slight counter-clockwise rotation of the cradle member 33, against the bias of the tension spring 46. This is possible because of the high amount of inertia stored in the movable contact arm assembly when tripping occurs. The hook-like extension 37 is therefore resiliently deflected slightly, permitting the movable contact arm to engage the contact arm stop 23a carried by the frame 23, and permitting the hook-like extension 37 of the cradle 33 to enter the slot 30a and to become engaged under a portion of the contact arm 20, retaining it in open circuit position.

The hook-like extension 37 is preferably constructed integral With the cradle member 33, as shown particularly in FIGURE 4. This provides a high degree of strength of these parts, and also eliminates the necessity for the fabrication of a separate part to act as a latch and the assembly operations necessary to assemble it with respect to the cradle member. It will also be observed that the operating spring 46 serves the dual purpose of operating the mechanism, and also of providing a resilient spring force to permit the inter-engagement of the contact arm 20 with the retaining hook 37.

In an actual test, an 800 ampere circuit breaker of the type shown herein was subjected to a short circuit current of over 30,000 amperes, asymmetrical, in repeated tests, first with the circuit breaker in the closed condition, the

short circuit being applied by means of a separate connecting device, and also repeated with the circuit breaker in the open condition and being closed in on the short circut. In each case, the movable contact arm became interlocked with the hook member 37 of the cradle, maintaining the movable contacts in open circuit position.

It will be seen that we have provided a simple and effective means for maintaining movable circuit breaker contacts in open position following automatic opening operation of the circuit breaker.

What we claim as new and desire to secure by Letters Patent of the United States is:

An electric circuit breaker comprising an insulating casing, at least one relatively stationary contact carried by said insulating casing, at least one movable contact movable between open and closed circuit positions with respect to said stationary contact, a movable contact arm for moving said movable contact between said open and closed circuit positions said movable contact arm being pivotally supported with respect to said casing, operating means for operating said movable contact arm between said open and closed circuit positions comprising a releasable cradle member pivotally supported in said casing, a pair of toggle links interconnecting said releasable cradle member and said movable contact arm, a manually operable handle member pivotally supported in said casing and movable between on and off positions, a tension type operating spring interconnecting said manually engageable handle member and the knee of said toggle, said cradle having an integral hook-like extensin, said cradle having a latched position in which said movable contact arm is retained in said closed position while said handle member is maintained in said on position, said cradle member also having a released position in which said movable contact arm is movable to open circuit position while said handle member is maintained in said on position, said hook-like extension of said cradle being disposed out of the path of movement of said movable contact arm while said cradle is in said latched position, said hook-like extension of said cradle being disposed in the path of movement of a portion of said contact arm when said cradle is in said released position, said hook-like extension having a cam surface thereon engageable by a portion of said contact arm, said portion of said contact arm acting on said cam surface to cam said cradle out of the path of movement of said portion of said contact arm against the bias of said operating spring sufficiently to permit said hook-like extension to enter said opening of said contact arm and into latched engagement with said portion of said contact arm to maintain said contact arm in said open circuit position and to prevent rebounding movement thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,932,706 Bodenschatz Apr. 12, 1960 

